A new control method for dimmable high-frequency electronic ballasts

A new control technique has been developed for high-frequency dimming of fluorescent lamps using phase-sensing of ballast output stage current to regulate lamp power. This approach has the following ballast design implications: (i) dimming to 1%; (ii) ignition at any dim setting; (iii) end-of-life detection; (iv) multiple lamp management; (v) no heating or current transformers required; (vi) no op-amps required; (vii) immunity from lamp negative incremental impedance effects; (viii) reduction of PCB interconnects and IC pin requirements; and (viii) minimum changes needed to adapt nondimming ballast for dimming. The result is a high-performance dimming solution with a significant cost reduction. A complete dimmable ballast has been built that incorporates a new integrated circuit verifying all of these features.